Porous bodies are notoriously difficult to satisfactorily interiorly electroplate. The problem intensifies with increasing diminishment of the void spaces involved, about which the plating deposit is desired to be made on the enclosing wall surfaces thereof. This is particularly so in cases where the body to be interiorly plated is a porous electrode intended for usage electrochemically and, typically, containing an abundance of exceedingly fine, internal body-traversing pores, oftentimes of miniscule size on the order of 10 microns and less to as small as even 0.1 micron or so.
Frequently, as with electrodes, the plating is only wasted and not needed or wanted (and may even be deleterious) on the exposed faces of the porous body to be plated. Also, standard electroplating techniques tend to cause a build-up of plating deposit on the exterior surfaces of the porous bodies, especially around and about pore egress sites. This is often serious enough to engender pore blocking, a seriously disadvantageous, if not fatal condition, when electrodes are involved. Further, normal means utilized to interiorly plate porous bodies are not always effectively efficient in leaving only conservatively but adequately thin deposit layer(s) on the enclosed surfaces to be plated. This is economically objectionable or even defeating when plating expensive coatings, such as those laid of silver as are often made for catalytic effect on the more base and less costly metal bodies of porous electrodes for electrochemical applications.
Attempts to preclude or circumvent the mentioned handicaps and shortcomings have not met with general success. And, they often require resort to awkward and/or complicated procedures to avoid or minimize one or more of the indicated problems. For example, it has been proposed to pump plating both through the porous body to ameliorate laying of internal coatings, the implementation of such sort of operation being not easy or straightforward and also not entirely reliable for realizing desired attainments. Illustrative of previous efforts in the area of present interest are U.S. Pat. Nos. 3,359,469 and 3,787,244 plus Canadian Pat. No. 921,111.